A devoutly religious mother of two ailing children has moved with her family to a mansion on the English coast. Her two children both suffer from a rare photosensitivity disease that renders them extremely vulnerable to sunlight, prompting the rule of having only one door open in the house at a time. When one of the children claims to see ghosts, Grace at first believes her newly arrived family of eccentric servants to be responsible, but chilling events and visions soon lead her to believe that something supernatural is indeed going on.